Existing pneumatic fan drive systems typically include a two-piece air cylinder, a piston rod, and a piston. Typically, the piston is slidable within the air cylinder with the piston rod attached to the air cylinder. Also, the air cylinder typically has a thin-walled stainless steel construction. As is known in the art, the stainless steel construction typically is resistant to corrosion. However, drawing stainless steel to a sufficient depth can produce cracks, scars, scratches, or various other imperfections in the stainless steel. These imperfections can cause substantial wear on components, e.g. seal rings, which slide across the surface of the air cylinder. Also, the surface finish and the thin-walled construction of the air cylinders can be easily damaged if dropped or otherwise mishandled during shipping.
One known air cylinder is mounted to a piston rod that has an end portion configured for attachment to the air cylinder. In particular, the end portion of the piston rod is comprised of an annular ledge and a threaded shaft with an axial slot, which is offset from the ledge by a predetermined distance for attaching the air cylinder to the piston rod. The air cylinder typically is comprised of a cylinder member and a separate washer member spot-welded to one end of the cylinder member. Furthermore, the washer member has a center hole with the threaded shaft of the piston rod extending therethrough. The washer member is sandwiched between the annular ledge of the piston rod and a nut fastener applied to the threaded shaft.
Moreover, the washer member typically includes a tab portion for providing additional support along the axial direction and preventing the air cylinder from spinning on the piston rod. This tab portion typically extends from the washer member into an axial slot formed in the threaded shaft of the piston rod. The tab portion of the washer member typically does not overlap the cylinder member and therefore typically is thinner than the overlapped portions of the washer member and cylinder member. For this reason, the axial slot in the threaded shaft is offset from the annular ledge by a distance generally equal to the recess or decrease in thickness for the tab portion. In that way, the ledge and the threaded shaft can respectively support the washer member and the tab portion.
It is thus highly desirable to provide a single-piece air cylinder for use in conjunction with existing piston rods for a pneumatic fan drive system and increasing the life of seal rings for those systems.